1. Field of the Invention
The present invention relates to a manufacturing process of a semiconductor device and, particularly, it relates to a metal-polishing liquid in a wiring process of a semiconductor device.
2. Description of the Related Art
In development of a semiconductor device, a representative of which is a semiconductor integrated circuit (hereinafter, referred to as LSI), for miniaturization and speeding up, densification and higher integration by finer downsizing and lamination of a wiring are required and, in recent years, as a metal for wiring, LSI using copper having a low wiring resistance has been developed and, as the technique therefore, various techniques such as Chemical Mechanical Polishing (hereinafter, referred to as CMP) have been used.
CMP is the technique for planarizing irregularities on a wafer surface produced by lamination. A general method of CMP is to apply a polishing pad on a circular polishing platen, impregnate a polishing pad surface with a polishing liquid, push a surface of a substrate (wafer) against a pad and, in the state where a predetermined pressure (polishing pressure) is applied from a back, rotate both of a polishing platen and a substrate, and flatten a surface of a substrate by a generated mechanical friction.
A metal-polishing liquid used in CMP generally contains abrasives (e.g. alumina, silica) and an oxidizing agent (e.g. hydrogen peroxide, persulfuric acid), and it is thought that a substrate surface is polished by oxidizing a metal surface with an oxidizing agent and removing the oxidized film with abrasives.
However, when CMP is performed using such the metal-polishing liquid containing solid abrasives, a polishing flaw (scratch), phenomenon in which a whole polishing surface is polished more than necessary (thinning), phenomenon in which a polishing metal surface is not planar, only a central part is polished deeper, and a dish-like recess is produced (dishing), and phenomenon in which an insulating material between metal wirings is polished more than necessary, and a plurality of wiring metal surfaces form a dish-like concave part (erosion) occur in some cases. Particularly, in recent years, for further higher densification and higher integration, reduction in dishing is increasingly demanded. In addition, recently, for improving productivity, a wafer diameter at LSI manufacturing is being scaled up and, currently, a diameter of 200 mm or more is generally used, and manufacturing at a size of 300 mm or more has been began. With such the scale up, a difference in a polishing rate between a central part and a circumferential part of a wafer becomes larger, and improvement in in-planar uniformity has been increasingly demanded. Further, recently, in order that film peeling is not caused even when an insulating material having a low mechanical strength is used, a method by which a sufficient polishing rate is obtained even when polishing is performed under a low pressure is desired. In order to solve such the problems, a metal polishing liquid consisting of hydrogen peroxide/malic acid/benzotriazole/polyammonium acrylate and water without an abrasive has been proposed (e.g. see Japanese Patent Application Laid-Open (JP-A) No. 2001-127019). According to this method, a conductor pattern in which a metal film remains on a concave part is obtained, but there is a problem that a sufficient polishing rate is difficult to obtain.
On the other hand, a polishing agent containing an abrasive has a problem that although a high polishing rate is obtained, aggregation of abrasives occurs during polishing, and a polishing rate is lowered due to the aggregation.